PIN半导体探测器γ光子灵敏度标定

在室温下，该种探测器的暗流达到微安量级，即使在现有最强的γ辐射源下，输出的电流也仅有微安量级，信噪比只能达到约为1。以前使用的PIN半导体探测器，其γ光子灵敏度仅用理论计算值，计算值的可靠性与精度需实验标定检验，成功标定的关键就是如何提高探测器输出的信噪比。由于条件的限制，以前没有实际标定过。现在，利用PIN半导体探测器的暗流与温度有关这一规律，采用半导体制冷器降低探测器环境温度实现降低暗流的目的。     

频率在FFT谱上位置对加窗泄漏的影响

以前讨论ＦＦＴ谱的加窗泄漏时，都不考虑频率在ＦＦＴ谱上所处位置对泄漏的影响［２，４，５，６］。由于实际信号和窗函数在频域为卷积关系，所以应该考虑实际频率在ＦＦＴ谱上所处的位置。本文找出了单一频率成份在谱图上不同位置时，产生泄漏的一般规律，并提出了有效的修正方法。     

含橡胶的摩阻材料之摩擦机理浅谈

作者从含橡胶的摩阻材料的摩擦状况出发,对其摩擦机理提出了一个新的观点——气穴排空说,並进行了简单的实验论证。认为弹性材料在与刚性对偶在负荷下接触时,由于材料的弹性变形使接触面间空隙中的气体被排出或部分排出而形成真空状态,因此弹性体上除了受外加负荷之外,还增加了部分大气压力,因而摩擦力也随之增大。摩擦力增大的部分为: △F=f·△P 式中f为材料间的摩擦系数,△P为正压力增大部分,其值可表示为: ΔP=A_(app)·P_(ntm)· 此处A_(app)为表现接触面积;P_(ntm)为大气压强;η为排空率(％)。η受材料弹性模量,负荷及对偶表面状态等的影响。     

担载多孔Al_2O_3膜的制备

研究了溶胶－凝胶法在多孔陶瓷载体上制备多孔Ａｌ２Ｏ３膜的工艺条件。发现在孔直径为１．１和１．６ｕｍ的多孔陶瓷载体上必须经过多次重复浸渍干燥－焙烧过程，才能制备出担载均匀的多孔Ａｌ２Ｏ３膜。对溶胶和多孔陶瓷载体进行适当的化学改性后，能够减少浸渍－干燥－焙烧过程重复的次数。对Ａｌ２Ｏ３膜的孔径大小和透气性能进行了表征。     

新显色剂5—（对羧基苯偶氮）—8—羟基喹啉与U（Ⅵ）的显色反就…

研究了新显色剂５－（对羧基苯偶氮）－８－羟基喹啉与Ｕ（Ⅵ）的显色反应条件，在阳离子表面活性剂ＣＴＭＡＢ存在下，ＰＨ４．０－６．０缓冲介质中，形成稳定的红色络合物，最大吸收波长为４７０ｎｍ，ε＝４．３９×１０＾４，，含Ｕ（Ⅵ）量在０－５５μｇ／２５ｍｌ范围内符合比耳定律，结合ＴＢＰ萃淋树脂分离富集，并以ＣｙＤＴＡ、ＫＦ联合掩蔽，方法适用于岩石矿物中痕量铀的测定。     

Application of Ultrasonic Attenuation Measurements in the Studies on Macromolecular Conformational Behaviors

——Phase Behavior of the Aqueous Solution of Poly(vinyl methyl ether) Sensitive to Temperature and the Modification of the Behavior by Using Poly(acrylic acid) The phase behavior of the aqueous solution of poly(vinyl methyl ether) (PVME) sensitive to temperature and the modification of the behavior by using poly(acrylic acid) (PAA) have been studied by ultrasonic attenuation measurements and fluorescence probe techniques. It has been observed that PVME solution is transparent at room temperature and becomes turbid upon heating. The solution turns clear again as soon as the temperature is decreased to room temperature. The heating and cooling process can be repeated for many times. The phase behavior of the solution sensitive to temperature is attributed to the conformational changes of the polymer. PVME may adopt an open coil conformation at room temperature. With this conformation, the polymer is well miscible with the solvent, water, and thereby the system is a real solution. The polymer may adopt a compact coil conformation when the temperature is higher than a specific value, which is called the LCST (the lower critical solution temperature) of PVME. In this case, the polymer tangles to each other and forms various aggregates, which can scatter incident light and ultrasonic waves greatly, resulting in the phase separation. Introduction of PAA decreases the temperature sensitivity of the phase behavior of the polymer. The nature of the inhibition is attributed to the complexation of PAA with PVME and the strong hydrophilicity of PAA. Results from fluorescence probe studies are in accordance with those from ultrasonic attenuation measurements, indicating again that the ultrasonic attenuation method can be successfully used for the qualitative studies of polymer conformations and complexation between polymers.     

KI催化酯交换合成碳酸二正辛酯的研究

研究了碳酸二甲酯与正辛醇酯交换合成碳酸二正辛酯（DOC）的反应，比较了卤化钾与系列碳酸钾复合催化剂的性能，考察了物料配比、反应温度、反应时间诸因素对该反应的影响，得出了该反应的最佳工艺条件．结果表明，KI具有较好的催化活性和选择性；在最佳反应条件（常压、反应温度140℃、反应时间为4h、n（DMC）：n（n-OctOH）=1：4、催化剂用量为总重1．25％。）下，DMC的转化率为83．7％，DOC的收率为70．0％，DOC的选择性为83．7％，甲基辛基碳酸酯（MOC）的收率为13．7％．     

A Novel Diterpenoid from the Soft Coral Sarcophyton crassocaule

A novel hydroperoxide cembrane-type diterpenoid was isolated from the soft coral Sarcophyton crassocaule collected from the Xisha Islands in the South China Sea. The structure of 3 was established by spectroscopy and X-ray diffraction analysis,named as sarcophyocrassolide A. It exhibited strong cytotoxicity against the P-388 cell line with IC50 value of 0.1 μg/mL.     

Synthesis, Crystal Structure and AbsoluteConfiguration of （＋）-O-Phenyl Cyclophosphorodiamidate

The title compound, ( )-O-phenyl cyclophosphorodiamidate (C28H33N202P, Mr=460.53), has been synthesized and characterized by 31p NMR, 1H NMR and elemental analysis. X-ray diffraction analysis at 273(2) K indicates that it belongs to orthorhombic system, space group P212121 with a=11.518(4), b=13.449(4), c=16.539(5)A, V=2562(1)A3, Z=4, Dc=1.194g/cm3, F(000)=984 and μ(MoKα)=0.134mm-l. The structure parameters were refined by full-matrix least-squares on F2 to R=0.0459 and wR=0.0640. The flack χ parameter is 0.03(10), and the absolute configuration of the phosphorus atom in the title compound is S.